1. Field of the Invention
The present invention relates to an inverter apparatus that drives an electric motor for electrical vehicles (EV) that are driven by an electric motor, hybrid electric vehicles (HEV) that are driven using a combustion engine and an electric motor, or the like, and in particular, relates to a resonant inverter apparatus that carries out soft switching using a resonant circuit.
2. Description of the Related Art
FIG. 19 is a circuit diagram showing the structure of a collective resonant snubber inverter apparatus. The conventional resonant inverter requires six cross-terminal voltage sensors Vs1, Vs3, and Vs5, and Vs2, Vs4, and Vs6 that detect the cross-terminal voltages V1, V3, and V5, and V2, V4, and V6 of the plus side main switching elements Q1, Q3, and Q4, and minus side main switching elements Q2, Q4, and Q6; a zero voltage detecting device 8 that detects whether or not the cross-terminal voltages, V1, V3, and V5, and V2, V4, and V6 that have been detected by the cross terminal voltage sensors Vs1, Vs3, and Vs5, and Vs2, Vs4, and Vs6 are zero; a resonant current sensor Is4 that detects the resonant current I4 flowing into the resonant inductor Lr; load current sensors Is1, Is2, and Is3 that detect the load currents I1, I2, and I3 that flow into the motor (load) 1, and a resonant current arrival determining device 7 that determines whether or not the resonant current I4 is larger than a maximum value among the load currents I1, I2, and I3.
However, in the conventional technology described above, because there are a large number of sensors, there are the problems that the circuit structure becomes complex, and this is also disadvantageous in terms of cost.
In consideration of the problems described above, it is an object of the present invention to provide a resonant inverter apparatus that can make the number of sensors small and reduce the cost.
A first aspect of the present invention is an inverter apparatus comprising an inverter circuit (for example, the main circuit 2A in the embodiments) that supplies a direct current output by a power source (for example, the direct current source VB in the embodiments) to a motor (for example, motor 1 in the embodiments) after being converted to three-phase alternating current; a resonant circuit (for example, auxiliary circuit 2B in the embodiments) that is connected to the output terminal of the inverter circuit; and a control circuit (for example, control circuit 3 in the embodiments) that controls the resonant circuit and the inverter circuit. The inverter circuit comprises a three phase main circuit in which three main circuits, one for each phase (for example, the main circuit for the 2U phase in the embodiments) are connected in parallel, wherein, in a main circuit, a plus side main switching element (for example, the plus side main switching element Q1 in the embodiments) that is connected to the plus terminal of the power source and the minus side main switching elements (for example, the minus switching element Q2 in the embodiments) that is connected to the minus terminal of the power source are connected in series, and the plus side switching element and the minus side switching element are connected in parallel to diodes (for example, the diodes D1 and D2 in the embodiments); resonant capacitors (for example, the capacitors C1 to C6 in the embodiments) that are connected in parallel to the plus side main switching element and the minus side main switching element in each circuit for each phase; and load current sensors (for example, the load current sensors Is1, Is2, and Is3 in the embodiments) that detect a load current (for example, I1, I2, and I3 in the embodiments) flowing between main connection points (for example, the main connection points PSU, PSV, and PSW in the embodiments), at which the plus side main switching element and the minus side main switching element in each circuit for each phase are connected together, and the motor. The resonant circuit comprises a three-phase auxiliary circuit in which three auxiliary circuits, one for each phase (for example, the auxiliary circuit for the phase 3U in the embodiments), are connected in parallel, wherein, in an auxiliary circuit, the outflow auxiliary switching elements (for example, the outflow auxiliary switching element block B7 in the embodiments) and the inflow auxiliary switching elements (for example, the outflow auxiliary switching element block B8 in the embodiments) that allow a current to pass only in one direction are connected serially, and the auxiliary connection points (for example, the auxiliary connection points PHU, PHV, and PHW in the embodiments) that connect the outflow auxiliary switching elements and the inflow auxiliary switching elements in each auxiliary circuit for each phase are connected to the main connection points; and a resonant inductor (for example, the inductor Lr in the embodiments) that is connected in parallel to the auxiliary circuits for each phase. The control circuit comprises a resonant current arrival determining device (for example, the resonant current arrival determination device 7 in the embodiment) that determines whether or not the resonant current (for example, the resonant current I4 in the embodiments) in the resonant circuit is larger than the load current detected by the load current sensor, and in the case that it is larger, outputs an arrival determination signal (for example, the arrival determination signal I in the embodiments); a drive signal generating device (for example, the drive signal generating device 6 in the embodiments) that generates a main drive signal (for example, the main drive signals S1 to S6 in the embodiments) that turns OFF the plus side main switching elements and the minus side switching elements when the resonant current arrival determining device has output an arrival determination signal, generates an auxiliary drive signal (for example, the auxiliary drive signals S7 to S12 in the embodiments) that turns ON the corresponding outflow side auxiliary switching element and the inflow side auxiliary switching element in the resonant circuit at a predetermined timing, and generates an auxiliary drive signal that turns OFF the outflow side auxiliary switching element and the inflow side auxiliary switching element auxiliary switching element after a predetermined ON continuation time has passed from the redefined switching timing. A resonant current arrival determining device comprising a maximum value detecting device (for example, the maximum value detecting device 12 that detects the absolute value of the maximum value of the load current) that detects the absolute value of the maximum value of the load current, a counter setting value output device (for example, the counter setting value output device 13 in the embodiments) that outputs a counter setting value corresponding to the maximum value; and a counter calculating device (for example, the counter calculating device 14) that outputs the arrival determination signal after the passage of a time interval that depends on the counter setting value output by the counter setting value output device after the drive signal generating device outputs a predetermined switching timing signal.
Due to having this structure, the maximum value detecting device detects the absolute value of the maximum value of the load current detected by the load current sensors in the inverter circuit, the counter setting value output device outputs the counter setting value that depends on the absolute value of the maximum value of the load current, and after the drive signal generating device outputs a predetermined switching timing signal, the counter calculating device outputs an arrival determination signal after the passage of a time interval that depends on the counter setting value output by the counter setting value output device.
In addition, when the resonant current arrival determining device outputs an arrival determination signal, the drive signal generating device generates a main drive signal that turns OFF the plus side main switching element and the minus side main switching element that are to be made non-conductive next.
Therefore, the resonant current sensor for detecting resonant current, which is necessary in conventional technology, becomes unnecessary.
In addition, according to the conventional method, because the response speed of the current sensor is very slow, equivalent to several xcexc seconds, it is very difficult to use for measuring a resonant circuit that operates at several xcexc seconds, and the error with respect to actual current was extremely large.
However, according to the structure described above, because the resonant current arrival determining device outputs the arrival determination signal based on the load current that changes extremely slowly in comparison to the resonant operation in the resonant circuit, the problem of the response speed of the current sensor does not occur, and in addition, because the analogue to digital conversion (A/D conversion) of the sensor output is reduced and timing control of the resonant operation can be realized with digital processing, the integration becomes simple, and size and weight reductions can be attained. In addition, because of the reduction in the use of current sensors that make the introduction of noise into the output signals easy, the influence on control by noise can be made small.
The second aspect of the present invention is the resonant inverter apparatus according to the first aspect wherein the drive signal generating apparatus comprises a delay circuit (for example, the delay circuit 11 in the embodiments) that, after the passage of a predetermined time interval after the resonant current arrival determining device outputs an arrival determination signal, generates a delay timing signal that turns ON the plus side main switching element and the minus side main switching element that are to be made conductive next.
According to this structure, the delay circuit generates a delay timing signal that turns ON the plus side main switching element and the minus side main switching element to be made conductive after the passage of a predetermined amount of time after the arrival determination signal is output by the resonant current arrival determining device.
Therefore, along with the resonant current sensor that detects the resonant current and the power source voltage sensor that detects the power source voltage, the cross terminal voltage sensor that detects the cross terminal voltage between the plus side main switching element and the minus side main switching element in each main circuit for each phase and the zero voltage detecting device that detects whether or not the cross terminal voltage detected by the cross terminal voltage sensor is zero become unnecessary.
Therefore, in the inverter apparatus, cross-terminal voltage sensors and resonant current sensors for soft switching do not have to be newly provided, and it becomes possible to form the inverter apparatus using only a digital circuit that generates a signal that follows the timing of the resonant operation. Therefore, the inverter apparatus can be made small and light weight, and in addition, the cost of the inverter apparatus can be decreased.
The third aspect of the invention is the resonant inverter apparatus according to the first and second aspects, wherein the inverter circuit comprises a power source voltage sensor (for example, the power source voltage sensor VBs in the embodiments) that detects the power source voltage (for example, the power source voltage Vx in the embodiments) output by the power source, and the counter setting value output device calculates the counter setting value based on the maximum value detected by the maximum value detecting device and the power source voltage detected by the power source voltage sensor.
According to this structure, the counter setting value output device calculates a counter setting value that depends on the power source voltage, not just the maximum value detected by the maximum value detecting device. In other words, the counter setting value that has been set based on the absolute value of the maximum value of the load current is compensated depending on the power source voltage.
Therefore, the size of the initial resonant current that forces conduction in the auxiliary circuit during the resonant operation can be controlled so as to attain the optimal value that depends on the power source voltage. That is, in the case that the value of the inductor is fixed, the slope of the resonant current that flows into the inductor changes when the resonant current rises due to the power source voltage. Thus, by detecting the power source voltage along with the maximum value of the current of the load current, the conduction time that the inductor requires to attain the initial resonant current necessary for resonance can be set to the optimal value. Thereby, reliable zero voltage switching can be realized. Moreover, in the case that a battery is used as a power source for an EV, HEV, or the like, the power source voltage sensor is already installed for use in the remaining charge control of the battery, and thus the power voltage sensor does not have to be newly provided, and the influence on the apparatus cost is small.
A fourth aspect of the present invention is an inverter apparatus comprising an inverter circuit that provides a direct current output by a power source after being converted to a three phase alternating current, a resonant circuit that is connected to the output terminal of this inverter circuit, and a control circuit that controls this resonant circuit and the inverter circuit. The inverter circuit comprises a three phase main circuit in which three main circuits, one for each phase, are connected in parallel, wherein, in a main circuit, a plus side main switching element connected to the plus terminal of the power source and a minus side main switching elements connected to the minus terminal of the power source are connected serially, and diodes are connected in parallel to the plus side main switching element and the minus side main switching element; a resonance capacitors connected to the plus side main switching element and the minus side main switching element in each phase of each circuit are connected in parallel; and a load current sensor that detects the load current flowing between main connection points that connect the plus side main switching element and the minus side main switching element in each phase of each circuit, and the motor. The resonance circuit comprises a three phase auxiliary circuit in which three auxiliary switching elements, one for each phase, are connected in parallel, wherein, in an auxiliary switching element, an outflow side auxiliary switching element and an inflow side auxiliary switching element that cause the current to flow only in a single direction, are connected serially, and the auxiliary connection points at which the outflow auxiliary switching element and the inflow auxiliary switching element in each auxiliary circuit for each phase are connected to the main connection point; a resonance inductor connected in parallel to each auxiliary circuit for each phase, and a resonance current sensor (for example, the resonance current sensor Is4 in the embodiments) that detects the resonant current flowing to the inductor. The control circuit comprises a resonant current arrival determining device that determines whether or not the resonant current detected by the resonant current sensor is larger than the load current detected by the load current sensor, and in the case that it is larger, outputs an arrival determination signal; and a drive signal generating device that generates a main drive signal that turns OFF the plus side main switching element and the minus side main switching element that are to be made non-conductive next when the resonant current arrival determining device outputs an arrival determination signal, generates an auxiliary drive signal that turns ON the outflow side auxiliary switching element and the inflow side auxiliary switching elements of the resonant circuit at a predetermined switching timing, and generates an auxiliary drive signal that turns OFF the conductive outflow side auxiliary switching element and the inflow side auxiliary switching element in the resonant circuit after the passage of a predetermined ON continuation time from the predetermined switching timing. The drive signal generating device comprises a delay circuit that generates a delay timing signal that turns ON the plus side main switching element and the minus side main switching element that are to be made conductive next after the passage of a predetermined time interval after the resonant current arrival determining device outputs an arrival determination signal.
Due to this structure, the delay circuit generates a delay timing signal that turns ON the plus side main switching element and the minus side main switching element that are to be made conductive next after the passage of a predetermined time interval from the point in time that the arrival determination signal is output by the resonant current arrival determining device.
Therefore, the cross terminal voltage sensor for detecting the cross terminal voltage of the plus side main switching element and the minus side main switching element in each main circuit for each phase and the zero voltage detecting device that detects whether or not the cross terminal voltage detected by the cross terminal voltage sensor is zero become unnecessary. Therefore, the cost of the resonant inverter apparatus decreases.
A fifth aspect of the invention is an inverter apparatus comprising inverter circuit that supplies a direct current that is output by a power source after being converted to a three phase alternating current, a resonant circuit connected to the output terminals of this inverter circuit, and a control circuit that controls this resonant circuit and the inverter circuit. The inverter circuit comprises a three phase main circuit in which three main circuits, one for each phase, are connected in parallel, wherein, in a main circuit, a plus side main switching element that is connected to the plus terminal of the power source and the minus main switching elements that is connected to the minus terminal of the power source are connected in series, and the plus side switching element and the minus side switching element are connected in parallel to diodes; resonance capacitors that are connected in parallel to the plus side main switching element and the minus side main switching element in each main circuit for each phase; load current sensors that detect a load current flowing between main connection points, at which the plus side main switching element and the minus side main switching element in each circuit for each phase are connected together, and the motor; a cross terminal voltage sensors (for example, the cross terminal voltage sensors Vs1, Vs3, and Vs5 in the embodiments) that detect the cross terminal voltages (for example, the cross terminal voltages V1, V3, and V5 in the embodiments) of the plus side main switching element and the minus side main switching element in each main circuit for each phase; and a power source voltage sensor that detects the power source voltage output by the power source. The resonant circuit comprises a three-phase auxiliary circuit in which three auxiliary circuits, one for each phase, are connected serially, wherein, in each auxiliary circuit, the outflow auxiliary switching elements and the inflow auxiliary switching elements that allow a current to pass only in one direction are connected in parallel, and the auxiliary connection points that connect the inflow auxiliary switching element and the outflow auxiliary switching element in each auxiliary circuit for each phase are connected to the main connection points; and a resonant inductor that is connected in parallel to the auxiliary circuits for each phase. The control circuit comprises a voltage difference calculating device (for example, the voltage difference calculating device 10 in the embodiments) that calculates the difference voltage, which is the difference between the power source voltage and the cross terminal voltage detected by each of the cross terminal voltage sensors; a zero voltage detecting device (for example, the zero voltage detecting device 8 in the embodiments) that detects whether or not the difference voltage and the cross terminal voltage are zero, and in the case that they are zero, outputs a zero voltage detection signal (for example, the zero voltage detection signals z1 to z6); and a drive signal generating device that generates a main drive signal that turns ON the plus side main switching element and the minus side main switching element that are to be made conductive next when the zero voltage detecting device outputs the zero voltage detection signal, generates an auxiliary drive signal that turns ON the outflow side auxiliary switching element and the inflow side auxiliary switching element at a predetermined switching timing, and generates an auxiliary drive signal that turns OFF the conductive outflow side auxiliary switching element and the inflow side auxiliary switching element after the passage of a predetermined ON continuation time from the predetermined switching timing.
Due to having this structure, the cross terminal voltage sensor for each phase detects the cross terminal voltage of the plus side main switching element and the minus side main switching element in each main circuit for each phase, the power source voltage sensor detects the power source voltage output by the power source, and the voltage difference calculating device calculates the difference voltage, which is the difference between the power source voltage detected by the power source voltage sensor in the inverter circuit and the cross terminal voltage detected by the cross terminal voltage sensors in each phase.
Therefore, in comparison to the conventional technology, it is possible to reduce the number of voltage sensors by two.
A sixth aspect of the invention is a resonant inverter apparatus according to claim 1 wherein the inverter circuit comprises a cross terminal sensor that detects the cross terminal voltage of the plus side main switching element and the minus side main switching element in each main circuit for each phase and a power source voltage sensor that detects the power source voltage output by the power source. The control circuit comprises a voltage difference calculating device that calculates the difference voltage, which is the difference between the power source voltage and the cross terminal voltage detected by each of the cross terminal voltage sensors and a zero voltage detecting device that detects whether or not the difference voltage and the cross terminal voltage are zero, and in the case that they are zero outputs a zero voltage detection signal. A drive signal generating device that generates a main drive signal that turns OFF the plus side main switching element and the minus main side main switching element that are to be made non-conductive next when the resonant voltage arrival determining device outputs an arrival determination signal, generates a main drive signal that turns on the plus side main switching element and the minus side main switching element that are to be made conductive next, generates an auxiliary drive signal that turns ON the outflow side auxiliary switching element and the inflow side auxiliary switching element at a predetermined timing, and generates an auxiliary drive signal that turns OFF the outflow side auxiliary switching element and the inflow side auxiliary switching element that are to be made non-conductive next after the passage of a predetermined ON continuation time from the predetermined switching timing.
According to this structure, the cross terminal voltage sensor for each phase detects the cross terminal voltage of the plus side main switching element and the minus side main switching element in the main circuit for each phase, the power source voltage sensor detects the power source voltage output by the power source, and the voltage difference calculating device calculates the difference voltage, which is the difference between the power source voltage detected by the power source sensor in the inverter circuit and the cross terminal voltage detected by the cross terminal voltage sensor for each phase.
Therefore, in comparison to conventional technology, the number of voltage sensors can be decreased by two.
In addition, like the first aspect, the drive signal generating device generates a main drive signal that turns OFF the plus side main switching element and the minus side main switching element that are to be made non-conductive next when the resonant voltage arrival determining device outputs an arrival determination signal.
Therefore, the resonant current sensors for detecting the resonant current, which have been necessary in the conventional technology, become unnecessary.
A seventh aspect of the invention is a resonant inverter apparatus of the sixth aspect wherein the counter setting value is calculated based on the maximum value detected by the maximum value detecting device and the power source voltage detected by the power source voltage sensor.
According to this structure, in the structure of the sixth aspect, the counter setting output device calculates a counter setting value that depends on the power source voltage not just the maximum value detected by the maximum value detecting device. In other words, the counter setting value that is set based on the absolute value of the maximum value of the load current is compensated depending on the power source voltage.
Therefore, the size of the initial resonant current is conducted into the auxiliary circuit during resonant operation can be set at the optimal value that depends on the power source voltage. That is, in the case that the value of the inductor is fixed, the slope of the resonant current flowing into the inductor rises due to the power source voltage. Thus, by detecting the maximum value of the current of the load current along with the power source voltage, the conducting time required by the inductor to attain the initial resonant current necessary for resonance can be set to an optimal value. Thereby, reliable zero voltage switching can be realized.